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Battery life is an issue for many types of robots. But it is especially challenging for robots operating in outer space. A new initiative under NASA’s “Tipping Point” program hopes to solve this and make smaller robots available for missions that weren’t within reach before, including night missions on the moon.
NASA awarded a $5.8 million contract to Astrobotic, Bosch, the University of Washington (UW), and WiBotic to overcome challenges of charging robots on the moon. Astrobotic is the main contractor as its CubeRover ultralight rover will be heading to the moon aboard the Peregrine lunar lander in 2021. Roughly the size of a shoebox and weighing less than 5 pounds, teams of CubeRovers can potentially scout locations on the moon’s surface.
Under this new partnership, WiBotic will be developing wireless charging systems and energy monitoring base stations for lunar robots, including the CubeRover. Bosch researchers will be contributing software expertise in wireless connectivity, and UW will contribute its Sensor Systems Lab to support realistic lunar environment testing and validation of mechanical enclosures that can withstand the moon’s harsh environment. WiBotic spun out of UW in 2015.
WiBotic already specializes in wireless charging, but so far has been designing its solutions for commercial, industrial and military robots that operate here on Earth. Its systems operate in dusty, dirty environments, but certainly nothing compared to what the moon has to offer. The wireless charging system’s receiver will be integrated with the CubeRover, while the transmitter will reside on the Peregrine lunar lander. Ben Waters, CEO and Co-founder, WiBotic, said the space-qualified system for the CubeRover will be based on its existing system.
“The primary thing in this process is leveraging existing designs, but changing components and enclosures, and perhaps architecture, so they’re radiation hardened,” he said. “Certain components will fail if you don’t use, for example, a microcontroller that’s radiation hardened. But there are various SKUs of a radiation-hardened microcontroller, so it’s mainly component selection.”
Lunar landers and large space exploration vehicles are typically powered by solar arrays or small nuclear reactors. Smaller systems, such as the CubeRover, sometimes aren’t big enough to carry their own dedicated power supplies. They could be tethered to a larger vehicle, but the tether would restrict mobility and be susceptible to lunar dust (regolith). A lunar night lasts up to 14 days, and temperatures can drop to -208 degrees Fahrenheit, which makes charging via solar arrays obsolete.
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“Bringing wireless power technology to the surface of the moon and beyond is a game-changer in the way space robotics systems have traditionally interacted,” said Cedric Corpa de la Fuente, electrical engineer for planetary mobility at Astrobotic. “For instance, by removing dependencies to solar charging, a new wide range of opportunities for smaller and lighter systems becomes available for missions that were not within reach before – such as survival of lunar night missions.”
Waters said passive cooling will be another change to the system as “fans don’t get you very far in the vacuum of space.” The connection ability also needs to be flexible as the moon’s surface often isn’t flat. WiBotic’s current systems can charge a robot even without making contact or dock with perfect alignment.
“From a technical perspective, it comes down to heat, surviving regolith and environmental conditions that the charging system could be exposed to. The system will also be launched on a rocket, so there will be massive vibration,” said Waters. “This is often the most-overlooked aspect of anything sent to space – the amount of force getting through the Earth’s atmosphere. Just getting there is a massive challenge, but once you get there you have all these things to contend with.”
Other challenges include designing the robust circuits and integration with the CubeRover. Waters said there will be about a year and a half of testing followed by almost a full year of testing. The prototype system will be sent to NASA, which will test it inside one of its simulation facilities.
“Moon dust is very fine and tends to stick to surfaces because it gets electrically charged. The UW team is tackling the fundamental research question of how dust particle size and composition affects power transfer efficiency,” said UW lead researcher Joshua Smith, a professor in both the Paul G. Allen School of Computer Science & Engineering and the Department of Electrical & Computer Engineering. “We plan to take an approach that is a hybrid of science and engineering: We will develop a synthetic moon dust that is consistent with known relevant properties, but that represents the worst case for our wireless power transfer system.”
How wireless charging works
WiBotic’s existing wireless charging systems consist of four primary hardware components: a transmitter unit, transmitter antenna coil, onboard charger unit and receiver antenna coil. Here’s how WiBotic explains its technology:
“The transmitter unit uses any available power source (AC or DC) to generate a high frequency wireless power signal. The signal travels through a coaxial SMA cable to the transmit antenna coil where it generates both electrical and magnetic fields. The coil can be mounted vertically in a wall station, horizontally in a drone landing pad (or floor mat), or in just about any other orientation to make it convenient for the robot as it arrives for a charge.
“The transmitter unit recognizes any incoming robot equipped with an onboard charger unit and receiver antenna coil and automatically ramps up to deliver the right amount of energy. Conveyed through air, water or other non-conductive materials, the energy is then collected by the receiver antenna coil on the robot and conveyed to the onboard charger. The onboard charger converts the signal back into a DC voltage and controls battery charging functions to safely replenish a wide range of batteries.
“To deliver wireless power, the transmitter first checks to be sure a robot is within range. The system is so flexible that even robots with completely different battery voltages can share the same transmitter unit. It automatically recognizes each robot and adjusts charge parameters accordingly.”
Lunar robots a proving ground
Space is the next frontier for WiBotic, which already works with underwater robots, mobile robots, and drones on Earth. Waters said the company’s longer-term vision is to pioneer a lunar wireless power grid to supply energy for a wide range of both manned and unmanned vehicles, irrespective of their individual battery types, voltages or required power levels.
“This is only the first step in creating a common infrastructure of wireless charging stations and Fleet Energy management software to be deployed across the surface of the moon,” he said.
Waters also said there’s an opportunity wirelessly charging robotic arms in space. “JPL and NASA have experienced some of the robotic arms having a limited lifetime in space compared to operating on Earth,” he said. Eliminating mechanical actuators with feedthrough for charging could be a future opportunity.”
WiBotic is hiring “a few folks” to work on the lunar robots system in a more focused manner, while maintaining everything on its existing commercial business.
“It’s definitely exciting [to be working on space products],” said Waters. “A lot of us at WiBotic have strong personal interest in space. We track SpaceX launches and other space-related developments. We’ve been super impressed with what NASA leadership has said about the ARTEMIS project and how much thought goes into this.”